The present invention relates to a thin film coating technique. More particularly, the invention relates to a thin film coating technique for applying a thin film to the surface of a substrate.
Generally, a printed-circuit board used in electronic devices such as computers and the like is constituted by an insulating substrate and a circuit pattern of copper or the like formed on one of or both sides of the insulating substrate.
Such a printed circuit board can be produced through the following manufacturing process:
a layer of stratified material composed of a light-sensitive resin (photoresist) layer and a light-transmissible resin film (protective film) for protecting the layer is laminated by thermocompression-bonding onto an electrically conductive layer provided on an insulating substrate. Thermocompression-bonding lamination is carried out in mass production by a thin film coating apparatus called a "laminator". Thereafter, a circuit-pattern film is formed on the stratified material, and the light-sensitive resin layer is exposed to light through the circuit-pattern film and light-transmissible resin film for a predetermined time. After the light-transmissible resin film has been peeled off by a separating device, the exposed light-sensitive resin layer is developed to form an etching mask pattern. Then, unnecessary parts of the conductive layer are removed by etching, after which residual parts of the light-sensitive resin layer are removed, thereby completing the printed-circuit board.
The thin film coating apparatus used in the aforementioned printed-circuit board manufacturing process is arranged to automatically laminate the stratified material by thermocompression-bonding. For example, in a thin film coating apparatus as described in commonly assigned Japanese Unexamined Patent Publication No. 60-71229, thermocompression-bonding lamination is carried out as follows:
A web of the stratified material continuously wound on a feed roller of the thin film coating apparatus is fed to the forward end of the surface of a substrate by main vacuum plates. Each of the main vacuum plates has a stratified-material-feeding surface provided with a plurality of suction holes for applying suction to the stratified layer. The main vacuum plate moves to the surface of the substrate while applying suction to the web of stratified material to thereby feed the stratified material. The forward end of the web of stratified material fed to the substrate is tacked temporarily by thermocompression-bonding to the conductive layer of the insulating substrate by an arc-like tack portion provided on the feeding-direction forward end of the main vacuum plate. The forward end of the web of stratified material can be held to the tack portion by a sub-vacuum plate which moves close to and away from the feeding passage of the web of stratified material. The conveyance-direction forward end of the substrate is detected by a sensor (at a detection position) provided along the conveyance passage in front of the tacking position where tacking is carried out. The conveyance-direction forward end of the substrate stops in response to a detection signal produced by the sensor after being conveyed from the detection position to the tacking position. After the conveyance-direction forward end of the substrate has stopped at the tacking position, the tack portion is moved close to the conveyance passage to perform the tacking operation.
After the completion of the tacking, the main vacuum plate moves away from the tacking position.
Next, each of the thermocompression-bonding rollers is moved from the standby position where the roller does not touch the tacking portion (main vacuum plate) so as to come into contact with the web of stratified material at the tacking position where the forward end thereof is tacked. The standby position of the thermocompression-bonding roller is closer to the conveyance passage of the substrate than the tacking position. The thermocompression-bonding roller rotates at the tacking position for the double purpose of laminating the stratified matter onto the surface of the substrate by thermocompression-bonding and conveying the substrate.
After a predetermined length of the stratified material has been laminated by thermocompression-bonding, the stratified material is cut into a predetermined length corresponding to the size of the substrate by the cutting device.
Subsequently, the feeding-direction rearward end of the stratified material cut by the cutting device is thermocompression-bonding-laminated onto the substrate by the thermocompression-bonding roller.
Thereafter, the thermocompression-bonding roller is moved from the tacking position to the standby position, thereby completing thermocompression-bonding lamination.
The aforedescribed conventional thin film coating apparatus is arranged to move the tack portion (main vacuum plate) close to the conveyance passage of the substrate after the conveyance-direction forward end of the substrate has stopped at the tacking position. Therefore, the time required for completing the tacking operation after the stopping of the substrate is long. Accordingly, a problem arises in that thermocompression-bonding-laminating time is long.
Further, in the conventional thin film coating apparatus the thermocompression-bonding roller is moved from the tacking position to the standby position after the rearward end of the stratified material is thermocompression-bonding-laminated to the surface of the substrate. More particularly, the thermocompression-bonding roller moves from the tacking position (i.e., in the Y direction) so as to be separated from the conveyance passage of the substrate. Next, the thermocompression-bonding roller moves to the standby position in the same direction as the conveyance direction of the substrate (i.e., in the X direction). With this arrangement, the time required for moving the thermocompression-bonding roller from the tacking position to the standby position after thermocompression-bonding lamination is long. Accordingly, a problem arises in that the thermocompression-bonding-laminating time of the stratified material is long.
In addition, a problem arises in that in the conventional thin film coating apparatus the productivity is low in manufacturing printed-circuit boards because the thermocompression-bonding-laminating time of the stratified material is long, as described above.